Conventionally, stand-type image readers (stand-type scanners) are used to read media such as business forms used in financial institutions or the like. An image captured by the image reader is converted into electronic data, and the electronized data is used to perform character recognition by principally using image optical character recognition (OCR) or to perform seal impression collation by superimposing seal-impression images onto each other. The image reader does not have a light source, and captures an image by using external light. Therefore, various shadows are included in a captured image according to installation environment. These shadows can be removed by performing calibration (initial adjustment) when the image reader is installed. An example of an image reader that performs the calibration above is disclosed in Patent Document 1 listed below.
Patent Document 1: Japanese Laid-open Patent Publication No. 2002-342752